This invention relates generally to the programming of programmable read-only memories, such as erasable programmable read-only memories (EPROMs).
In the prior art, EPROMs are generally programmed using high DC voltages. For example, when programming an EPROM, in order to program a floating gate of the EPROM, a voltage of 15 volts is placed on the gate, a voltage of 5 volts is placed on the drain and a voltage of 0 volts is placed on the source. When erasing the EPROM, a negative voltage with high negative magnitude (e.g. 11 volts) is placed on the control gate. The programming and erasing results, for example, from current tunneling or current injection. See, for example, Y. Yamauchi, et al, "A 5V-Only Virtual Ground Flash Cell with An Auxiliary Gate for High Density and High Speed Application", IEDM, 1991, p. 11.7.1, or N. Kodama, et al., "A Symmetrical Side Wall(SSW)-DSA Cell for a 64Mbit Flash Memory", IEDM, 1991, p. 11.3.1.
The programming methods of the prior art have several drawbacks. For example, a high voltage source is needed to perform the programming. Also, EPROMs programmed according to the prior art often lack in endurance.